1. Field of the invention
The present invention relates to a photosensitive recording material using a photosensitive resin which is employed in various arts such as a printing art.
2. Description of prior arts
A photosensitive recording material comprises a layer of photosensitive resin (photopolymer). Since the photosensitive resin varies in its molecular structure by exposure to light or the like so that the photosensitive resin is made soluble or insoluble in a solvent, a visible image (pattern) can be formed on the photosensitive recording material by utilizing said phenomenon. Accordingly, the photosensitve recording material has been used widely as a printing plate (e.g., a PS lithograph, a resin relief plate, etc.), a photo resist (e.g., a dry film resist), a prepress proof and and a "dot to dot work" lith-type film according to the purpose in various fields involving a photography and a printing art in which a visible image is required, and a plate processing art.
For instance, a photosensitive recording material used for color proofing to foresee clolor condition, color tone, etc. of the finished printing takes a structure comprising a support (hereinafter also referred to as a temporary support), an intermediate layer of an organic polymer and a photosensitive resin layer, superposed in this order. In concrete, in the case of using the photosensitive recording material as an image-forming material (i.e., photosensitive transfer sheet) in a surprint process, a separation image is formed on the intermediate layer (peel layer) of the recording material through exposure and development, and the separation image is transferred onto an optionally chosen support to prepare a color proofing sheet having the separation image.
The color proofing sheet is used for checking the color of finished printing when the color proofing is actually performed, so that the hue of the separation image formed on the photosensitive recording material (color image-forming material) is desired to be as sharp as possible.
For obtaining a colored image on the photosensitive recording material, there has been generally carried out a process comprising the steps of mixing an organic pigment having excellent properties in clearness of color, coloring affinity, and a range of hues, and the like, with a photosensitive resin, solvent, etc. to prepare a coating solution, applying the solution onto the aforementioned intermediate layer to obtain a recording material, exposing the recording material, and removing a soluble resin from the resin layer by development (i.e., patterning) with a developing solution. In order to satisfying the wide usage for the photosensitive recording material, a pigment in which a metal is chelated is now paid much attention because said pigment is favorable in the above-mentioned various properties.
The metal-chelated pigment is insoluble (i.e., stable) in the above-mentioned coating solution, because the pigment has an anionic group (e.g., a carboxylic acid group or a sulfonic acid group) as a substituent in its molecule, and has a chelated monovalent or divalent metal ion such as sodium or potassium to form a metal salt. Therefore, when a photosensitive resin layer is formed using such pigment, other layer (intermediate layer) is prevented from being colored, whereby an image having sharp hues can be obtained.
However, in some cases, the chelation of the metal ion in the pigment is not completely formed, and a portion of a pigment is free from the chelation. The free pigment is soluble in the coating solution. Accordingly, when a photosensitive resin layer is formed using the coating solution containing such soluble pigment, the pigment tends to permeate the intermediate layer together with the solvent in the stage of applying the solution onto the intermediate layer. As a result, the intermediate layer is likely stained with the pigment. Thus, so-called color-fogging is produced on the intermediate layer.